From 78d44b824ed04dd1553c55c5b839c9a55cbcaf4e Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 17 Aug 2023 11:19:13 -0600 Subject: cgroup: Avoid -Wstringop-overflow warnings Change the notation from pointer-to-array to pointer-to-pointer. With this, we avoid the compiler complaining about trying to access a region of size zero as an argument during function calls. This is a workaround to prevent the compiler complaining about accessing an array of size zero when evaluating the arguments of a couple of function calls. See below: kernel/cgroup/cgroup.c: In function 'find_css_set': kernel/cgroup/cgroup.c:1206:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] 1206 | cset = find_existing_css_set(old_cset, cgrp, template); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ kernel/cgroup/cgroup.c:1206:16: note: referencing argument 3 of type 'struct cgroup_subsys_state *[0]' kernel/cgroup/cgroup.c:1071:24: note: in a call to function 'find_existing_css_set' 1071 | static struct css_set *find_existing_css_set(struct css_set *old_cset, | ^~~~~~~~~~~~~~~~~~~~~ With the change to pointer-to-pointer, the functions are not prevented from being executed, and they will do what they have to do when CGROUP_SUBSYS_COUNT == 0. Address the following -Wstringop-overflow warnings seen when built with ARM architecture and aspeed_g4_defconfig configuration (notice that under this configuration CGROUP_SUBSYS_COUNT == 0): kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] This results in no differences in binary output. Link: https://github.com/KSPP/linux/issues/316 Signed-off-by: Gustavo A. R. Silva Reviewed-by: Kees Cook Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/cgroup') diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 85e723abd9e2..2604db9cb13a 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -907,7 +907,7 @@ static void css_set_move_task(struct task_struct *task, #define CSS_SET_HASH_BITS 7 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS); -static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) +static unsigned long css_set_hash(struct cgroup_subsys_state **css) { unsigned long key = 0UL; struct cgroup_subsys *ss; @@ -1048,7 +1048,7 @@ static bool compare_css_sets(struct css_set *cset, */ static struct css_set *find_existing_css_set(struct css_set *old_cset, struct cgroup *cgrp, - struct cgroup_subsys_state *template[]) + struct cgroup_subsys_state **template) { struct cgroup_root *root = cgrp->root; struct cgroup_subsys *ss; -- cgit